A multi-function machine is a handheld oscillating power tool common in this field, and its working principle is that an output shaft makes oscillating movement about its own axis. Therefore, after a user installs different work heads on a free end of the output shaft, for example, a straight blade, a circular saw blade, a triangular grinded tray and a shovel-type scraper, many different operation functions can be achieved, for example, saw, cut, grind, scrape and so on, to adapt to different work demands.
Specifically, refer to FIG. 1 and FIG. 2, an oscillating power tool 100′ includes a case 1′, an output shaft 2′ extending out of the case 1′, a motor 11′ disposed in the case 1′ and a spindle 4′ driven by the motor 11′. One end of the spindle 4′ is connected with an eccentric shaft 41′ offset to its axis Y, and the eccentric shaft 41′ is mounted thereon with a bearing 8′ having a spherical outer surface 81′. A fork 7′ is disposed between the spindle 4′ and the output shaft 2′, one end of the fork 7′ is pivotally connected to the output shaft 2′, and a pair of arms 71′ on two sides of the bearing 8′ are formed on the other end. An axis X of the output shaft 2′ is substantially perpendicular to the axis Y of the spindle 4′, and the outer surface 81′ of the bearing 8′ closely touches the inner surfaces of the arms 71′ of the fork 7′. When the spindle 4′ rotates about its axis Y, through coordination between the bearing 8′ and the fork 7′, the output shaft 2′ is driven to make oscillating movement about its own axis X within a certain oscillating angle, thereby driving a tool head 6′ mounted on the output shaft 2′ to oscillate.
When the above oscillating power tool 100′ is working, the bearing 8′ is driven by the eccentric shaft 41′ to rotate around the axis Y of the spindle 4′. And axial movement of the fork 7′ fastened on the output shaft 2′ is limited, therefore, the output shaft 2′ of the oscillating power tool 100′ can only oscillating within a fixed oscillating angle range. During use, the user usually hopes that the oscillating power tool 100′ can output different oscillating angles, to meet more working condition applications. For example, when the oscillating power tool 100′ is used to install the straight blade on different-hardness wood materials to open a slot, if the wood materials have lower hardness, it is feasible that the output shaft 2′ outputs a common small oscillating angle; when the wood materials have higher hardness, at a smaller oscillating angle, it is not easy to discharge sawdust, so that the straight blade is easy to get stuck, and at this point, the output shaft 2′ is required to output a larger oscillating angle. Evidently, the oscillating power tool 100′ cannot meet such a demand.
In the technical solution disclosed by the application in the patent application document with International Publication Number WO2012041211A1, the bearing is pushed through a toggle and a connecting rod to horizontally move along an eccentric shaft, to cause the fork to match the bearing in different positions, so that the output shaft has different oscillating angles. The position setting of the bearing in the technical solution is changeable, and when the fork and the bearing complete the matching and operate, the fork's producing reciprocating oscillating movement may bring about a reactive force to the bearing, to cause the bearing to be forced to be easy to move on the eccentric shaft, resulting in that limiting of the toggle and the connecting rod may cause failure with make the operation unstable.
Therefore, it is indeed necessary to provide an improved oscillating power tool, to solve the above problems.